The accident happened on a stretch of the route that is a familiar irritant to regular Amtrak riders. Trains from Boston zip through Massachusetts and Rhode Island, only to slow down after passing New Haven. That section of the corridor is owned by the state of Connecticut, which does not maintain it to high-speed standards.

The tracks where Friday’s accident happened use old-fashioned “jointed rail”: much of the route in Connecticut also uses an electrical system from 1907 to power locomotives. In other parts of the Northeast Corridor, including in Massachusetts, trains run on continuously welded track and use a modern electrical system. The section where the crash occurred actually contains two more sets of tracks, which could have been used to reroute trains after the accident, but they are out of service, part of a repair project that has been limping along since 1991.